Metal-working machine



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Aug. 30, 1927.

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Patented Aug. 30, 1927.

UNITED STATES PATENT OFFICE. 1

IBENGT M. W. HANSON, DECEASED, LATE OF HARTFORD, CONNECTICUT; BY EINAR A. HANSON AND CLARENCE E. WHITNEY, EXECUTORS, OF HARTFORD, CONNECTICUT.

METAL-WORKING MACHINE.

Application filed March 18, 1926. Serial No. 95,765.

This invention relates to metal working As an instance of a: use to which the improvements of the present invention may be applied, reference may be had to a machine for grinding thread cutting hobs, that is, hobs of the ty e having circumferential ribs transversely dated to form teeth, the ribs being parallel to each other. It is to be understood, however, that the present disclosure is by way of illustration and is not restrictive of the invention, it being obvious that the invention is susceptible of various modifications and embodiments, certain of the novel features may be employed in other relations than herein disclosed, and the terms here used are merely terms of, description and not terms .of limitation.

The general aim of the invention is to provide an improved machine by means or which circumferentially grooved members, and particularly thread cutting hobs, may be formed expeditiously and economically and with the greatest precision.

-More particularly, the aim of the invention is to provide an improved machine by means of which thread cutting hobs may be ground with an accuracy and at a high rate of production.

A further aim of the invention is to provide an improved machine having various features of novelty and advantage and{which is characterized by its relative simplicity, considering the numerous functions which it performs; by the smoothness and lack of vibrations or other disturbing factors with which the various movements are brought about; by the facility with which the machine may be set up; and the manner in which it is controlled to bring about the various movements in the proper sequence and relation.

Other objects will be in partobvious and in part pointed out more in detail herein- Figs. 2, 3 and 4, when placed side by side, constitute a top planview of the entire machine wlth'parts broken away; Fig. 2 being a top plan of the left hand end of the machine; Flg. 3, the central portion; and Fig.

.4, the right hand end;

Fig. 5 illustrates the mechanism through which the work is indexed, the mechanism beingsh wn as it would appear looking at the left and end of the rocking bed, portions of the casing enclosing this mechanism being removed or broken away;

Fig. 6 is a View taken vertically on sub: stantially line 6-6 of Fig. 2 and looking in the direction of the arrows;

Fig. 7 is a vertical sectional view-taken substantially on line 7-7 of Fig. 3 and lookmg in the direction of the arrows;

Fig. 8 is a view taken on line 8-8 of Fig. -3 and looking in the direction of the arrows;

Fig. 9 is a: diagrammatic layout showing the driving mechanisms andconnections for the various 'instrumentalities;

1 Fig.10 is a schematic view of the arrange ment through which the driving mechanisms are controlled;

Fig. 11 is a detail view, in side elevation, of the trip device associated with the feed cam and which device sets intooperation the cycle of movements of certain instrumentalities;

Fig. 12 is a sectional view taken 'on line 1212 of Fig. 11;

Fig. 13 is a horizontal sectional view taken substantially on line 13-13 of Fig. 11;,

Fig. 14 is a longitudinal sectional view through the shaft 142 and the parts associated therewith;

Fig. 14 a is a view taken on of Fig. 14; a

Fig. 15 isa: face view of the disk 151;

Figs. 16, 17 and 18 are diagrammatic views each showing a thread cutting hob being ground by a grinding wheel;

Fig. 17-a is a view showing the manner in which a groove is ground when the stepped wheel shown in Fig. 17 is employed;

Fig. 18-a is a series of views showing, in side elevation, the relation between the work and the respective serrations of the grinding wheel shown in 18.

In order that the following detailed description may be more readily understood,

a brief statement of the general construction and operation of the machine will be given. The machine is provided with a fixed bed or base A on which is normally fixed a spindle B which carries a tool, this 1 tool, in the present illustrative disclosure, being in the form of a grinding wheel C preferably havin a plura ity of circumferential parallel ri s or serrations which, in cross section, correspond to the grooves desired to be ground into the work. In the present instance, the ribs correspond in cross section to a screw thread which the hob operated upon is adapted to cut. The machine is also provided with a rocking bed D preferably mounted on knife ed es E and on this rocking bed is provide a work holder including a work spindle F adapted to rotatably support the work operated upon. The work spindle F is continuously driven in timed relation to a relieving cam G which acts to rock the bed D through a rocking beam H so as to give the desired radial clearance to the .teeth on the hob. The work holder is moved axially of the spindle with a step by step movement by brought about-through a differential mecha-,

nism- M when the lead screw is "turned to index the work. After each indexing movement of the work, the rocking bed D is swung by means of a device or cam N (also acting through the rocking beam E) so as to bring the work into engagement with the tool and, after the work has been brought into engagement with the tool, it is gradually fed into the tool by means of a feed cam O which also acts through the rocking beam. The cam N, the feed cam and the escapement clutch Kare controlled through an escapement ratchet clutch P by a trip mecha nism R associated with the feed cam. After the work has been fed to the proper depth into the tool, the cam N moves the work away from the. tool; rotation of the feed cam is stopped; the lead screw indexes the work holder 'one step; then the cam N again moves the work into enga ement with the tool; the relieving cam rocks the work in accordance with the desired radial relief and, during the grinding operation.

the feed'cam feeds the work into the tool.-

and this sequence of operations is repeated until all of the grooves of the hob have been so that taper hobs ma be operated upon, and a ca T is provi ed for eflect-. ing an axial relief on the teeth of the work.

Referring now to the detailed construction of the machine, and particularly to Figs. 1 and 4, A designates the base of any suitable construction having ways 11 on which is mounted for adjustment towards and away from the work holder, a tool slide 12 carrying an adjustable {bearing 13 in which is journalled a tool spindle B. This tool s indle is continuously driven in any suitab e manner, as by means of a belt 15 passing about a drive pulley 16, guide pulleys 14 and 17, and a pulley on the grinding w eel spindle. The guide pulley 17 is adjustable and is spring pressed; for example, it may be supported on a swinging bracket 19 carried by a slide 20 mounted for horizontal adjustment ,on a slide 21 which may be vertically adjusted by a screw 22. 23 is a spring connected to the bracket 19 for holding the guide pulley 17 against the belt. The tool slide may be adjusted towards and away from the axis about which the rocking bed D rocks, by a screw 24; on the forward end of which is a hand wheel 25 provided with a suit-able scale for indicating theadjustment of the tool slide.

In some instances, where the work to be operated upon is in the form of a thread cutting hob having flutes of relatively large spirality, it may be found of advantage to incline the grinding wheel in accordance with the angle of helix of the flutes. To this end, the bearing 13 is adjustable about a horizontal axis passing diametrically through the grinding wheel. This axis is indicated by the point 28, see Fig. 1. On an upstanding-portlon 29 of the slide 12 are grooves 30 curved about the axis just referred to, and passing through the flanges of the-bearing racket 13 are bolts 31, the heads of which adjustably engage in the grooves.

In the present instance, the tool is shown as being in the form of a inding wheel having a plurality of circumge rential, parallel and continuous serrations 33, each serration corresponding in cross section tothat of the grooves to be ground, which shape, in the case of a thread cutting hob, corresponds to the cross section of a screw thread. The grinding wheel is generally similar to those illustrated and described in my co-pending application Serial No. 18,835, filed March 27, 1925. In that embodiment shown in Fig. 16, the serrations are identical, that is, they are of the same size and diameter. In the event a grinding wheel thus constructed is em ployed to operate upon a straight fluted hob, as shown, the first serrations 33- '-a assuming that the Work is indexed step by step in the direction of the arrow 34, will grind thesuccessive grooves with which it is brought into contact until it has been worn down, whereupon the second serration 33b will do the major portion of the rinding, and, after the second serration 33 is worn down, the third serration 330.comes into play, and so on.

The grinding wheel may be arranged so.

that each serration will grind a small increment' from each groove on the work. For instance,- as shown in Fig. 17, the grinding wheel may have'serrations of increasing size, in the present instant, the serrations being of substantially the same shape and of progressively increasing diameter so that they will progressively grind small portions from the sides and roots of the grooves. The-serration 33a', being the smallest one, will grind a small increment -a from each groove (see Fig. 17a) the next serration 33-b will grind an additional lncrement 35b' from each groove, and so on until the final serration will take a final increment, thereby grinding the thread to the exact size andv shape.

In the event thegrinding wheel shown in Fig. 16 is employed to grind a thread cutting hob having spiral flutes and with the teeth radially relieved, as illustrated in Figs. 18 and 18a, increment grinding will also be effected as will hereinafter be described more in detail. 7

In any event, the serrations of the grinding wheel are preferably arranged and constructed so that a cooling fluid may pass, during the grinding operation, through spaces provided between the grinding wheel and each of the ribs on the work, as described inthe said Hanson application Serial No.

18,835. To this end, the grooves between the serrations are relatively deeper than the active grinding faces of the serrations. By

preference, the serrations of the grinding" wheel are spaced apart .a distance other than that between adjacent grooves on the work so that the serrations will grind non-adjacent grooves. In the accompanying illustrations, the grinding serrations are shown as being spaced apart so that they will operate at any one instance upon every other groove in the work but it is, of course, obvious that they may be otherwise spaced apart.

longerthan would be the case if the wheel were provided with but a single grinding edge. The speed at which the grinding operations are preformed is greatly in-' creased, the time consumed in maintaining the grinding wheel in condition for accurate grinding is considerably reduced, and the likelihood of errors in the work on account of wear of the wheel. is eliminated to a great extent.

. The rocking bed, indicated by the letter D, extends along the forward edge of the base A and has, adjacent its left end, a rearwardlyl extending arm 36 on which is mounted t e gear box '47; The rocking bed has, at its extreme left hand end, a rearwardly extending portion 36' carrying a gear box or casing in which is. housed the escapement clutch K and Geneva motion device L. The rocking bed is mounted for rocking movement on suitable knife edges E. Mounted on the longitudinally extending portion of the rocking bed for sliding movement substantially parallel to the axis about which the rocking bed is swung, is a work holder which includes a main slide 37 mounted on ways 38, a supplemental slide 39 adapted to be adjusted ongitudinally on the main slideby a screw 40, a head stock 41 and an adjustable tail stock 42 on the supplemental slide 39. J ournalled in the head stock is the work spindle F. This spindle may have a Very-lim- I bearings, isintermittently driven through the escapeinent clutch K and Geneva motion device L. The clutch K, the device L and other parts of the drive for the lead screw are enclosed in a casing 43 carried by the arm 36 of the rocking bed.

, The relieving cam, which is designated by the letter G, is fixed to a shaft 46 journalled in a gear box 47 on the rearwardly extending leg 36 of the rocking bed (see Figs. 3 and 8). This cam, in rocking the rocking bed, acts through a rocking beam H pivoted on the gearbox 47, as at .49. For the purpose of obtaining radial reliefs of various kinds or extents on the work without providing a separate cam for each desired relief, there is provided between the cam and the rocking beam means for varying the action of the cam. This means, as shown most clearly in Fig. 8, includes a piece 50 pivoted to the gear box 47, as at 51, and carrying a roller 52 resting on the cam G. Journalled against longitudinal movement in the long and forwardly extending end of the rocking beam H is a screw 53 on which works a nut 54 carrying a roller 55 resting The lead screw, which is. mounted agalnst longitudinal movement in .suitable on the piece 50. The nut 54 may be adjusted towards and away from the pivot v51 by rotating the screw. The screw may be thus rotated-by means of a hand wheel 56 acting through bevel gears 57. When the roller is adjacent the pivot point 51, the cam will rock the bed but very slightly and effect a small radial relief. As the roller is adjusted away from the pivot point, the extent to which the bed is rocked is increased. A spring 57' may be employed to urge the roller 52 into engagement with the cam. The cam G may have one or more lobes or lands, two being shown by way of illustration. In the event no relief is to be given to the teeth on the work, the long end of the rocking beam may be raised out of the influence of the cam by turning down a screw 58 against a stop 59 (see Fig. 8).

During the grinding operation, the rocking bed is slowly swung downwardly and rearwardly so as to feed the work into the grinding wheel. This is done by means of a feed cam O fixed to a shaft 61 journalled in the rearwardly extending and relatively short arm of the rocking beam.. This cam, which is rotated in the direction of the arrow (Fig. 7) one complete revolutiolr during each period that the work and wheel are in engagement, is generally. an involute and has a high point 60. The cam O, as shownmost clearly in Fig. 7, is supported on a post 62 which rests upon the fixed bed A. The post is slidably supported insuitable bearings 63 carried by the rocking bed.

I For the purpose of changing the rate of feed of the feed cam without changing its rate of rotation, adjustable means may be interposed between the post 62 and the feed cam. This means, which is similar to that interposed between the relieving cam and the rocking beam, includes a piece 64 pivoted as at 65 and resting on a roller 66 carried by a nut 67 adapted to be adjusted on the top of the post by a screw 68. The cam O rides on an antifriction roller 69.

The instrumentalitly' 'for raising the work away from the whee preliminary to index.-

ing the work and then lowering the work' into engagement with the wheel after the work hasbeen indexed, may be, as shown in Figs. 3 and 8, in the form of an eccentric or cam N which is intermittently rotated 180 in timed relation to the feed cam and lead screws The cam N is fixed to a shaft 76 journalled in the gear box 47. About the eccentric N is a strap 77 having an upstanding rod or pitman 78, the upper end of which slides in a sleeve or hub 79 depending from the long arm. of the rocking beam. 'Adjustably carried by the rocking beam is a screw 80, the lower end of which is adapted to rest upon the top of the pitman 78. The screw 80 will be adjusted according to the diameter of the=work operated upon.

For the purpose of adapting the machine for operation upon a piece of work having a longitudinal contour, as in the, case where a ta ered hob is to be ground, a cam S is provi ed. This cam (herein termed the taper cam, for convenience) is fixed to a shaft 85 journalled in a casing 86 fixed to the lower end of the post 62, and on which post, as previously stated, is supported the feed cam O. The cam S rides upon a roller 87 journalled on the top of the fixed bed or base A the rocking beam about the upper end of the post 62 as a fulcrum. As the high point of the cam G moves into engagement with the roller 52, the long end of the rocking beam is raised, thereb swinging the rocking bed with the work older thereon slightly upwardly and forwardly, and, as-the high point of the cam G leaves the roller 52, the bed is moved downwardly and rearwardly in accordance with the relief to be given to the teeth. When the lifting cam N- is rotated 180 from the position shown inFig. 8, the work will be moved out of engagementwith the wheel and, on the next half revolution of this cam, the work will be moved into engagement'with the wheel. The feed cam O rotates in a direction to gradually move the work into the tool until the grooves have been ground to the desired depth and, at

which time, the high point 60 ofthe feed cam comes into play to move the work slightly away from the wheel and, at this time, the machine is tripped, as hereinafter described more in detail, to effect the lifting movement of. the rocking bed and the indexing movement of the work.

Reference may now be had to. the manner in which the work spindle, the lead screw, the axial relieving cam T, and the instrumentalities for rocking the rocking bed are driven. The driving mechanisms for these elements are. most clearlyshown in diagrammatic form in Fig. .9," and the connections,

through which the driving mechanisms are controlled. are shown diagrammatically in Fig. 10. Tracing first the drive for the work spindle, 90 designates what, for convenience, is termed a main shaft journalled in the gear box 47 and having a drive pulley 91 driven by a belt 92 (see Figs. 1, 3 and 6-). The belt 92 (see Fig. 1) passes about a pulley are fixed to a shaft 106.

93 which is driven through gears '94 and a belt 95 from the shaft. 96 journalled in the" base Aand having a drive pulley 97 adapted to be connected to a suitable source of power. Proper tension may be maintained on the belt 92 by a spring pressed idler pulley 98. The work spindle is continuously driven from the shaft 90 through gears 100 and 100, stub shaft 101, and gears 102, 103, 104 and 105. The gears 103 and 104 The gear 105 is fixed to a sleeve 107 journalled in, but fixed against longitudinal movement relative to, a bearing 108 on the rocking bed. The work spindle F is mounted in the sleeve for longitudinal movement relative thereto but 'is keyed to the sleeve so as to rotate therewith, as shown in Figs. 3 and 7.

The lead screw I is intermittently driven to index the work through the following driving connections. On the main shaft 90 is a gear meshing with a gear 116 ona shaft 117 on the lefthand end of which is a gear 118 which drives, through gear 119, shaft 120 and gear 121, a gear122. The opposite ends of the shaft 120are journalled in the gear boxes 43 and 47. This. gear 122 is continuously driven and is normally loose on a shaft 123. Fixed to, so as to rotate with, the gear 122 is a ratchet Wheel 124 which constitutes one element of the escapement clutch mechanism K. The

other element of this escapement mechanism includes a pawl 125 pivoted on a disk 126 fixed to the shaft 123'. The engagement of this pawl 125 with the continuously rotating ratchet 124 is controlled, as shown most clearly in Figs. 5 and 10, by a yoke 127 having a pair of diametrically opposite stops 128 adapted to be alternately brought into the path of travel of the pawl .125 so that the shaft 123 is intermittently rotated through an angle of 180. The escapement yoke 127 is fixed to a vertically movable rod 129, movement of which is controlled, as hereinafter described more in detail, by atrip mechanism associated with the feed cam O, and acting through the. escapement ratchet clutch P which controls the cam N for raising and lowering the rocking bed and which also controls rotary movement of the feed cam. For the purpose of insuring that the shaft 123 will stop in correct positions,

a spring pressed plunger 130 is providedfor engagement with notches 131 in the periphery of the disk 126.

Fixedto the intermittently operated. shaft 7 123 is a driver or cam disk 135 of the Geneva motion device L. On the face of this disk is a pair of diametrically spaced rollers 136 adapted to engage in the radial slots 137 of a driven member or wheel 138'fixed to a stub shaft 139. The slots 137, as shown by dotted lines in Fig. 5, arefour in number so that, upon each half revolution of the disk 135,

fixed on a shaft142. The gears 140 and 141 are in the ratio of one to four so that, upon each quarter revolution of the-shaft 139, the

shaft 142 will make one complete revolution. Power is transmitted from the shaft 142 to the lead screw I through three sets of gears 144a bc, 145wb-c and 146ab-cd, gear 146d being fixed to the lead screw. Gears 144a, 146b and 1460 are change gears. For the purpose of insuring that the head screw and the work-holder moved thereby are uniformly indexed upon actuation of the Geneva motion device, there is provided, as shown most clearly in Fig. 5, a single tapering notch 150 in the periphery of a disk 151 fixed to, so as to rotate with, the intermittently operated gear 141. Pivoted to the casing 43, as at 152, is a lever 153 having a pin 154 adapted to wedgedly fit in the notch 150. Connected by a pin and slot arrangement to the lever 153 is a lever 155 pivoted as at 156 and having a roller 157 resting on the periphery of the driver 135 of the Geneva motion device. The periphery of the-driver 135 is provided with two diametrically opposite lands 158. Upon each half revolution ofthe driver 135 a land 158 will raise the lever 155 thereby withdrawing the pin 154 from the notch 150 so that the Geneva motion device may be operated. After the driver 135 has made one complete revolution, the pin will drop back into the notch 150, as shown in Fig. 5, thereby insuring this driver is always stopped in the same position.

The manner in which the pattern or relief cam G is driven will now be described. In the event that a straight fluted thread cutting hob is operated upon, this relieving cam will be driven in timed relation to the work spindle F and the relation between the relieving cam and spindle will not be changed G is fixed, is driven through the shaft 106,

and differential or speed compensating mechanism M. This mechanism includes'a' ear fixed" on the shaft .106, a air of idlers 166, and a differential gear 16 The gear 167 drives a gear 168 fixed on a-shaft 169 having a gear 170 meshing with a gear 171 on the shaft 46. When a spirally fluted thread cuttinghob is ground, a shaft 172 fixed to the shaft 172. The change gears 178 will be selected in accordance with the spirality of the flutes of the work. When a straight fluted hob is to be ground, one of these change gears may be removed so that the relieving cam will not be affected by the indexing movement of the work holder. j

- hen a hob with right hand spiral flutes is operated upon, the angular relation between the relieving cam and the work spindle will he changed in one direction, and, when a-hob with left hand spiral flutes is operated upon, the relation between the relieving cam and work spindle will be changed in the other direction. To this end, there is provided between the shafts 175 and 176, a reversing mechanism which includes a gear 183 fixed to the one end of the shaft 175, gear 184 loose on the shaft 17 6, a bevel gear 185 meshing with each of these gears, and a clutch sleeve 186 splined for longitudinal movement on the shaft 17 6. When the clutch sleeve 186 is engaged with the gear 184, the drive from the shaft 175 to the shaft 176 is through the gears 183, 185 and 184 so that the shaft 172 carrying the idlers of the differential mechanism will be rotated in one direction. When the sleeve 186 is engaged with the gear 183, the gear 184 will run idle and the shafts 175 and 176 are directly connected so that the shaft 172 will be rotated in the opposite direction. The reversing mechanism just'described, the gears 178, and the gears 179 are housed within a casing 187 on the rear left hand corner of the rearwardly extending arm 36 of the rocking bed. The sleeve 186 is shifted by means of a lever 188 fixed to the upper end of a vertical shaft 189 which carries a in Figs. 1, 3 and 9, includes the cam T driven through gear 191 fixed to the relieving cam shaft '46, a gear 192 on a shaft 193, gears 194, shaft 195 and bevel gears 196, one of which is splined on a shaft 197 parallel to the work spindle. The shaft 197 is .journalled in, and moves with, the head stock 41. On this shaft 197 is a bevel gear 198 meshing with a gear 199 fixed on the. same shaft as is the axial relieving cam T. J ournalled in the head stock is a rock shaft 200 on one end of which is an arm 201 carrying a roller 202 resting on the cam T. On the other end of this rock shaft 200 is a yoke 203 connected to the collar or strap 204 engaging in a groove of a sleeve 205 fixed to the work spindle. When the cam T is rotated, it slightly reciprocates the work spindle axially in accordance with the desired axial relief. In case no axial relief is to be given to the teeth on the work, the roller. 202 is raised out of engagementwith the cam T by screwing down a screw 206 against. the short end of the lever or arm 201 (see Fig, 1). With the arrangement just described, it will be seen that, when the radial relieving cam G is rotated, the axial relieving cam T will be rotated in the same manner so that the axial and radial reliefs are properly co-ordinated.

The taper cam S is driven intimed relation to the lead screw as follows: The gear 185 is fixed to a shaft 208 extending into a gear casing 209 on the rear right hand corner of the arm 36 of the rocking bed. The

shaft has, within the casing, a gear 210 meshing with a gear 211 on a shaft 213 (see Figs. 3 and 7). Also journalled in the gear box 209 (see Figs. 7 and 8) is a shaft 214 driven through change gears 215. on this shaft 214 is a bevel gear 216 meshing with a gear 217 splined on a vertical shaft-218 havmg a worm 219 meshing with a worm wheel 220 (see Fig. 6) on a. shaft 85 which carries the taper cam S. The shaft 218 is parallel to the post 62 and is journalled in the casing 86 fixed to the lower end of the post. It will be noted that the action of the differential speed mechanism M through the reversing clutch 186 may be reversed without affecting the direction of rotation of the taper cam S; that is to say, the shaft 208 is rotated in the same direction when the sleeve 186 is engaged with either'the gear 183 or gear 184.

The lifting cam or eccentric N for moving the work out of engagement with the wheel preliminary to indexing the work and then lowering the work into the wheel, after the former has been indexed, is driven from the continuously driven shaft 117 through an escapement ratchet clutch P which includes a. gear 225 adapted to run loose on the shaft 76 on which the cam N is fixed. The gear 225 is continuously driven by a gear 227 on the shaft v117. The ratchet clutch referred to is generally similar to that which has been described in connection and 10).

controlled through the trip mechanism R associated with the feed cam O, as hereinafter described more in detail.

The drivefor the feed cam 0 will now be described. A shaft 240 is driven from the continuously driven shaft 106 through bevel gears 241. .On the shaft 240 is a gear 242 which drives, through gear 243, shaft 244 and gears 245, a shaft. 246 (see Fi s. 3,7 The shaft 246 extends through, and is journalled in, a bearing located at the I pivotal point of the rocking beam and carries gwithin a gear casing 247' on the rearward y extending and short end of the rocking beam) a bevel gear 248. Journalled in this casing 247 is a shaft 249 having at one end a bevel gear 250 meshing with the gear 248, and at its other end a gear 251 meshing with a gear 252 on a shaft 253 carrying a worm 254 (see Fig. 8) meshing with a worm wheel 255 fixed to the feed cam shaft 61 which is journalled in the short arm of the rocking beam. The gear 242 is adapted to be engaged with and disengaged from the continuously driven shaft 240 by means of a'clutc-h, 260 which may be of any suitable construction and the details of which are, therefore, not shown. It is suflicient to sa when the sleeve or collar 261 splined to t e shaft 240 is moved to 'one position, the clutch is engaged so that the ear'242 will rotate with the shaft 240 resu ting in the feed cam being driven and when the sleeve is in the other position, the gear 242 is loose on the shaft so that the feed cam will not be driven during the indexing movement of the work holder. The sleeve 261 is moved into and out of engaging position by ashipper lever 262 hav ing a pin 263 enga 'n in a cam groove 264 of the cam 230 an w ich cam is a part of one of the rotatable units of the escapement clutch P through which intermittent rotation of the lifting camN' is effected.

The operation of the niachine will be explained in connection with a description of the arrangement through which the sequence of movements of various instrumentali-ties are controlled, this arrangement being diagrammatically illustrated in Fig. 10. Assuming that the machine has been properl set up and the work has just been indexed: and then the liftingeccentric of cam N has been rotated 180 "to swin the bed rearwardly and downwardly, t ereby bringing the Work into engagement with the grinding wheel, the feed cam is automatically set'into rotation and, during. the inding of the grooves in the work with w ich the wheel is in engagement, this feed cam ers the work backwardly an into the grinding wheel. While this is gradually 'lowdownwardly.

takingplace, the radial relieving cam (Jr,

where such relief is desired, rocks the rocking bed up and down about the knife edges E in accordance with the niimber of flutes on the work and the extent of clearance desired. Also,.'where axial rlief is desired, the cam T is driven to slightly reciprocate the work spindle B axially within the head stock 41. When the grooves have been ground to the desired depth, the'high point of the feed cam 0 will ride onto the roller 69 and at this time the trip mechanism R '(see Figs. 10, 11 and 12) associated with the cam 0 will result in actuation of the e'scapement clutch P which will do three things: firsF-turn the lifting cam or eccentrio N 180 and thereby swing the rocking bed upwardly and forwardly to withdraw the work from the wheel; seconddisengage the clutch260, thereby stoppingrotation of the feed vcam O with its high point on the roller; and, third-Pset into operation a trip which controls the escapement clutch K'associated with the indexing mechanism for the work holder. The knock-off or trip mechanism R includes a tripping finger 270 carried by a plate 271 on the shaft 61 which carries the feed cam.- Fixed to the shaft 61 is a disk 272 carrying a spring pressed plunger 273 provided with a pin 274 engaging in a radial slot 275 in the plate 271.

ind the plunger 273 is a spring 276. Somewhat before the feed cam has completed a rotation, the end of this plunger will engage. the cam edge of a cam blo ck- 277 where y the plunger will be moved from the dotted line position to the full line position of Fig. '11. As'the feed cam completes a rotation, the plunger becomes free of the cam block 277, whereupon it is shot to the dot and dash line position of Fig. 11', causing'the plate 271 and the trip finer 270 to be thrown with a snap movement rom the full line position to the broken line position of Figs. 11 and 13. When this trip finger is thus thrown, it engages a finger 280 de ending from one end .of' a lever 281 pivote as at 282, thereby throwing-the lever from the full line to'jth'e dotted line position shown in Fig. 13. When the lever 281 is.

' yoke is raised. When the cam N is thus r y lifting the yoke 231 tated, itraises the long end of the rocking beam and thereby swings the. rocking bed upwardly and forwardly so that the work will b moved out of engagement with the wheel. At about the same time, the cam 230, whichrotates 180 with the shaft 76,

will throw the shipper lever 262 and thereby disengage the clutch 260, thus stopping rotation of the feed cam with its high point I on the roller 69.

287 are in the ratio of two to one so that, upon a half revolution of the gear 286, the

-' ear 287 will rotate a quarter of a revolution. When the gear 287 thus rotates, one of the lugs 288. will engage a pin 299 on a lever 300 and, through the following connection's, ment clutch K. These connections include a rock shaft 301 to which the arm 300 is fixed and having a second arm 302 connected by a link 303 to a crank lever 304 which, in turn, is connected to the rod 129 which carries the yoke 127. A lug 288 trips the yoke 127 just before the gear 287 completesits quarter revolution so as to insure that the work has been raised by the cam N out of engagement with the wheel before the work is indexed. When the yoke 127 is thus shifted, the pawl 125 is released from the upper stop 128, whereupon the pawl will engage the ratchet 124 causing rotation of the shaft 123. The extent of rotation of the shaft is limited, however, to 180 because the lower stop 128, which has been raised into the path of movement of the pawl, will disengage the latter from the ratchet when the pawl has been rotated a half revolution. Upon a half revolution of the shaft 123, the disk or driver 135 of the Geneva motion device L will rotate the driven member 138 a quarter of a revolution, resulting in the rotation of the lead screw through an angle which will step or index the work a distance equal that between adjacent grooves on the work.

The work now having been indexed, it is necessary to lower the work into engagement with the wheel and start the feed cam, and this is done in the following manner: Projecting from the face of the disk 126 of the escapement clutch K is a pair of cams or trips 310 into the path of movement of which a pin 311 has been moved when the knock-off or trip mechanism R threw the lever 281, as follows: Connected to the crank lever 284 by means of a rod 312 and an arm 313 is an oscillating shaft 314 having on its lower end a radially extending arm 315 carrying the pin 311. After the indexing movement of the work has been completed and before the shaft 123 comhalf revolution, one of the trips pletes 1ts 310 engages the pin 311 thereby rocklng the actuate the yoke 127 of the escape-' crank lever 284 in a direction to lower the yoke 231, whereupon the escapement clutch P will be engaged and the shaft 76 will make a half revolution, resulting in the eccentric or cam N lowering the rocking bed so that the work is brought into engage- 'ment with the wheel and also .resulting in the cam 230 engaging the clutch 260, whereupon the feed cam 0 will start to rotate. Also, when the crank lever 284 is thus thrown, the trip mechanism R is re-set, that is to say, the finger on the lever 281 is moved into the path of the tripping finger' 270. The grooves of the work, with which the serrations of the grinding wheel are now in engagement, will be ground to the desired diameter when the feed cam has completed .movementanto engagement with, and past,

the finger 280, the trip mechanism may be properly re-set; that is, the finger 280 may be moved to the full line position shown in Fig. 13 without any likelihood of this finger striking the tripping finger 27 0.

After the work has been ground throughoutthe desired length, the machine is automatically stopped as follows: The gear 100, which is constantly driven, is adapted to be engaged with, and disengaged from, the shaft 101 by means of a clutch 325 having a clutch sleeve 326 splined to the shaft 101.

Associated with this sleeve, as shown most clearly in Fig. 7, is a yoke 327 fixed on a rock shaft 328 journalled in, and extending to the front of, the rocking bed. On the forward end of this shaft 328 is a lever 329 connected by a link 330 (see Fig. 1) to a rod 331 shdably supported in arms 332 and 333, respectively, on the supplemental slide 39 of the work holder and the rocking bed.- On this rod is an adjustable dog 334. On the indexing movement succeeding the completion of the grinding of the final series of teeth on the hob (and at which time the lifting cam N is holding the work away from the wheel), the bracket or arm 332 will engage the dog 334, thereby moving the rod 331' and link 330 to the right, referring to Fig. 1, and this will result in turning the shaft 328 counterclockwise so that the clutch 325 is disengaged to stop rotation of the tripping finger 27 0 of the trip mechawork spindle and the feed cam 0. Since 1 

